@ravnic is such a purist. I am adventurous and I'd be ok with:
I do think there is lots of design space in expanding basic "land" boxes, but the more complicated your decisions are after the draft, the more like building (the mana base of?) a constructed deck the experience is. I like that draft decisions are bite-sized, and complicating the last step is not something I'm usually looking for in the interest of accessibility for my cube.
That said, maybe putting fixing in the draft is kind of extra steps already, and it would be fine to give everyone X fetches and Y shocks of their choice and reduce booster sizes to, say, 3x12. It's just logistically and economically (playing on paper) much easier to have a single or a copies of nonbasics, and there is something to be said for doing things the usual way, which players are comfortable with.